The present invention concerns improved petroleum fuel compositions. More particularly, it relates to gasoline and diesel fuel compositions having improved stability.
Petroleum motor fuels for internal combustion engines, particularly gasoline for spark ignition engines and diesel fuel for compression engines, are susceptible to formation of insoluble tars or gums upon exposure to atmospheric oxygen. During storage, gum formation is particularly severe in fuels derived from catalytic refining processes. Gum formation in gasoline is the result of oxidation and polymerization of unsaturated components, particularly dienes or highly unsaturated compounds, the resulting product being resinous gums. Similarly, diesel fuels form gums during storage. Some types of gums are soluble in the fuel and a residue is formed after the fuel has been evaporated. Thus, a buildup of gum can form on the fuel injection system. Moreover, insoluble solid particles can form when stocks containing dissolved gums are blended together. The particles can clog fuel filters and injection systems. When motor fuels are stored for any considerable period, an additive to inhibit oxidative gum formation is incorporated into the fuel.
It has been discovered that petroleum fuels, particularly motor fuels normally susceptible to oxidative gum formation, can be stabilized by incorporating certain organic heterocyclic molybdenum complexes. Molybdenum compounds are widely used in lubricants, but hereto have not been known to provide protection against gum formation in fuels for internal combustion engines.